Volcanic Gas Monitoring at Mount Baker

Regular monitoring of the temperature, gas chemistry, and gas emission at volcanoes with
relatively low activity levels can help scientists determine whether and how magma is moving
beneath
the volcano. These types of measurements have been made sporadically at Mount Baker since the
early 1970's.

In March 1975, gas emissions
and
temperatures increased dramatically at Mount Baker's Sherman Crater – almost half the glaciers
within the crater melted and the measured amount of released heat increased more than 10 times.
Fumarole temperatures reached "superheated" status and registered over 130 C° in some
areas
of Sherman Crater. Higher amounts of carbon dioxide and sulfur gases, assumed to be hydrogen
sulfide, were detected very shortly after the signs of activity increased in 1975, but emissions of
both
have decreased through time. Additionally, since the 1970's, the amount of heat released has
decreased and the distribution of hot zones within Sherman Crater has reorganized.

The gases at Mount Baker arrive at fumaroles area after having bubbled through and
interacted
with an extensive groundwater system that overlies the magma. Despite being "filtered" through
the
blanket of ground water, changes in the gas chemistry can point to periods when there is more
magma within the volcanic plumbing system. In contrast to most other volcanoes in the
Cascades,
gas emissions at Mount Baker are typically high enough to be measured with airborne techniques,
making such changes easier to detect. The existence of higher gas emissions, particularly the
observation of high CO2 over time, provides strong evidence for ongoing magmatic
activity at depth. Increases in the ratio of CO2 to other gases at Mount Baker
suggested that the increase in activity in 1975 resulted from an emplacement of
a
small amount of fresh magma into the mid-crust beneath the volcano, or potentially from opening
a
network fractures to a deeper reservoir of (more primitive) magmatic gases. The prevalence of deep long-period seismicity at Mount
Baker is also thought to be linked to movement of either magma or gases beneath the volcano.

The continued monitoring of gases, temperatures, and seismicity at Mount Baker is important
for
detecting changes in the deep system of magma and predicting volcanic unrest. Fumarole
samples
and gas emissions are measured every year or two, unless increases in seismicity or deformation
are
detected, which would cause much more frequent sampling to be carried out.